Semiconductor device, manufacturing method thereof, and semiconductor manufacturing apparatus

ABSTRACT

An a-Si film is patterned into a linear shape (ribbon shape) or island shape on a glass substrate. The upper surface of the a-Si film or the lower surface of the glass substrate is irradiated and scanned with an energy beam output continuously along the time axis from a CW laser in a direction indicated by an arrow, thereby crystallizing the a-Si film. This implements a TFT in which the transistor characteristics of the TFT are made uniform at high level, and the mobility is high particularly in a peripheral circuit region to enable high-speed driving in applications to a system-on glass and the like.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims priority of JapanesePatent Application Nos. 2000-255646 and 2001-202730, filed on Aug. 25,2000 and Jul. 3, 2001, the contents being incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. [Field of the Invention]

[0003] The present invention relates to semiconductor devices,manufacturing methods of the same, and semiconductor manufacturingapparatus, in particular, for being suitably applied to a so-calledsystem-on panel, in which a pixel region including thin film transistorsand a peripheral circuit region including thin film transistors areformed on a non-crystallized (amorphous) substrate such as a non-alkaliglass substrate.

[0004] 2. [Description of the Related Art]

[0005] A TFT (Thin Film Transistor) is formed on a very thin, fineactive semiconductor film. The TFT is examined to be mounted on alarge-screen liquid crystal panel or the like in consideration of recentdemands for an increase in area. In particular, applications to asystem-on panel and the like are expected.

[0006] On the system-on panel, polycrystalline semiconductor TFTs(especially polysilicon TFTs (p-Si TFTs)) are formed on anon-crystallized substrate such as a non-alkali glass substrate. In thiscase, as a popular method, an amorphous silicon (a-Si) film is formed asa semiconductor film, and then irradiated with an ultravioletshort-pulse excimer laser to fuse and crystallize only the a-Si filmwithout influencing the glass substrate, thereby obtaining a p-Si filmfunctioning as an active semiconductor film.

[0007] Excimer lasers which emit high-output linear beams coping with alarge area of the system-on panel have been developed. A p-Si filmobtained by excimer laser crystallization is readily influenced by notonly the irradiation energy density but also the beam profile, the stateof the film surface, or the like. It is difficult to form uniformly ap-Si film large in crystal grain size in a large area. A samplecrystallized by an excimer laser was observed with an AFM to find thatcrystal grains isotropically growing from nuclei produced at randomexhibited a shape close to a regular polygonal shape, projections wereobserved at a crystal grain boundary at which crystal grains collidedagainst each other, and the crystal grain size was less than 1 μm, asshown in FIG. 37.

[0008] In this manner, when a TFT is fabricated using a p-Si filmobtained by crystallization using an excimer laser, a channel regioncontains many crystal grains. If the crystal grain size is large, andthe number of grain boundaries present in the channel is small, themobility is high. If the crystal grain size at a channel region portionis small, and the number of grain boundaries present in the channel islarge, the mobility is low. Thus, the transistor characteristics of theTFT readily vary dependently on the grain size. In addition, the crystalgrain boundaries have many defects, and the presence of the grainboundaries in the channel suppresses transistor characteristics. Themobility of the TFT attained by All this technique is about 150 cm²/Vs.

SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide semiconductordevices including TFTs in which the transistor characteristics of theTFTs are made uniform at a high level, and the mobility is highparticularly in a peripheral circuit region to enable high-speed drivingin applications to peripheral circuit-integrated TFT-LCDs, system-onpanels, system-on glasses, and the like.

[0010] It is another object of the present invention to providesemiconductor devices in which the insufficiency of the output of anenergy beam, which outputs energy continuously in relation to time, iscompensated so that the throughput in crystallization of semiconductorfilms is improved, thereby realizing highly efficient TFTs whosemobility is high particularly in a peripheral circuit region to enablehigh-speed driving.

[0011] It is still another object of the present invention to providemanufacturing methods of such semiconductor devices.

[0012] It is still another object of the present invention to provideapparatus for manufacturing such semiconductor devices.

[0013] According to the first aspect of the present invention, there isprovided a method of manufacturing a semiconductor device in which apixel region having thin film transistors and a peripheral circuitregion are formed on a non-crystallized substrate, comprisingcrystallizing a semiconductor film formed in the peripheral circuitregion with an energy beam which outputs energy continuously along atime axis at least for the peripheral circuit region, thereby formingthe semiconductor film into active semiconductor films of the respectivethin film transistors.

[0014] In this case, the energy beam is preferably a CW laser beam, morepreferably, a solid state laser beam (DPSS (Diode Pumped Solid StateLaser) laser beam).

[0015] By crystallizing a semiconductor film with an energy beam whichoutputs energy continuously along the time axis, the crystal grain sizeis increased, e.g., the crystalline state of the semiconductor film isformed into a streamlined flow pattern having long crystal grains in theenergy beam scan direction. The crystal grain size in this case is 10 to100 times the size obtained by crystallization using a currentlyavailable excimer laser.

[0016] In the first aspect, each semiconductor film is preferablypatterned into a linear or island shape on the non-crystallizedsubstrate.

[0017] The crystallization technique using a CW laser has conventionallybeen studied in the SOI field, but a glass substrate has been considerednot to resist heat. When a glass substrate is irradiated with a laserwhile an a-Si film is formed as a semiconductor film on the entiresurface, the temperature of the glass substrate rises along with thetemperature rise of the a-Si film, and damage such as cracks isobserved. In the present invention, the semiconductor film is processedinto a linear or island shape in advance to prevent the temperature riseof the glass substrate, generation of cracks, and diffusion ofimpurities into a film. Even in forming the active semiconductor film ofa TFT on a non-crystallized substrate such as a glass substrate, anenergy beam which outputs energy continuously along the time axis from aCW laser or the like can be used without any problem.

[0018] In the first aspect, an energy beam irradiation positioningmarker corresponding to each patterned semiconductor film is formed onthe non-crystallized substrate.

[0019] This marker can suppress an irradiation position shift of theenergy beam. Supply of a stable continuous beam enables so-calledlateral growth, and a semiconductor film having large-size crystalgrains can be reliably formed.

[0020] In the first aspect, it is preferable that slits be formed ineach semiconductor film patterned on the non-crystallized substrate, orthin-line insulating films be formed on each semiconductor film, and thesemiconductor film be irradiated with the energy beam in an almostlongitudinal direction of the slits.

[0021] In this case, the slits or insulating films (to be simplyreferred to as slits hereinafter for convenience) block crystal grainsand grain boundaries which grow inward from the periphery incrystallization by irradiation of an energy beam. Only crystal grainswhich grow parallel to the slits are formed between the slits. If theregion between the slits is satisfactorily narrow, single crystals areformed in this region. In this manner, the channel region can beselectively changed into a monocrystalline state by forming the slits soas to set a region where large-size crystal grains are to be formed,e.g., the region between the slits as the channel region of asemiconductor element, e.g., thin film transistor.

[0022] In the first aspect, it is preferable that an irradiationcondition of the energy beam which outputs energy continuously along thetime axis be changed between the pixel region and the peripheral circuitregion, that a semiconductor film formed in the pixel region becrystallized with an energy beam which outputs energy pulses, and thesemiconductor film formed in the peripheral circuit region becrystallized with the energy beam which outputs energy continuouslyalong the time axis (more specifically, the semiconductor film formed inthe pixel region be crystallized, and then the semiconductor film formedin the peripheral circuit region be crystallized), or that thesemiconductor film formed in the peripheral circuit region becrystallized with the energy beam which outputs energy continuouslyalong the time axis, the crystallized semiconductor film be set as anactive semiconductor film, and a semiconductor film formed in the pixelregion be set as an active semiconductor film without any change.

[0023] Although positional controllability is important for either ofthe pixel and peripheral regions, any thin film transistor formed in theperipheral circuit region requires higher performance than that in thepixel region, and must be optimized in fabrication. For this purpose, anenergy beam which continuously outputs energy and can reliably form anactive semiconductor film having large-size crystal grains and make theoperation characteristics of respective thin film transistors uniform athigh level is applied particularly to the peripheral circuit region. Inthe pixel region where the required performance is low, the energy beamirradiation time is shortened, or a pulse-like energy beam is applied.In this way, the crystallization process is changed between theperipheral circuit region and the pixel region. Accordingly, a desiredsystem-on panel which very efficiently satisfies the requiredperformance of respective locations can be implemented.

[0024] According to the second aspect of the present invention, there isprovided a semiconductor device in which a pixel region having thin filmtransistors and a peripheral circuit region are formed on anon-crystallized substrate, wherein active semiconductor films of therespective thin film transistors constituting at least the peripheralcircuit region are formed into a crystalline state of a streamlined flowpattern having large crystal grains.

[0025] In this case, the active semiconductor film can be changed into alarge-crystal-grain state, and preferably a monocrystalline state alongthe streamlined shape of the flow pattern. For example, the channelregion of a thin film transistor can be changed into a monocrystallinestate. A high-speed-driving thin film transistor excellent in transistorcharacteristics can be implemented.

[0026] Besides, the semiconductor film is preferably formed over thenon-crystallized substrate with a buffer layer being interposed betweenthem. The buffer layer includes a thin film containing Si and N, or Si,O, and N. The density of hydrogen in the semiconductor film ispreferably 1×10 ²⁰/cm³ or less, more preferably, the density of hydrogenin the buffer layer is 1×10 ²²/cm³ or less.

[0027] By this construction, the transistor characteristics of the TFTscan be uniformized at a high level using crystallization with an energybeam that outputs energy continuously in relation to time. Further, theTFTs can stably be formed without generation of pinholes or peeling-off.Very highly reliable TFTs can be realized thereby.

[0028] According to the third aspect of the present invention, there isprovided a semiconductor manufacturing apparatus for emitting an energybeam for crystallizing a semiconductor film formed on a non-crystallizedsubstrate, wherein the semiconductor manufacturing apparatus can outputthe energy beam continuously along a time axis, and has a function ofscanning the energy beam to an object to be irradiated, and outputinstability of the energy beam has a value smaller than ±1%.

[0029] In this case, the output instability of the energy beam is set toa value smaller than ±1%, and more preferably noise representing theinstability of the energy beam with respect to the time is set to 0.1rms % or less. A stable continuous beam can therefore be supplied. Thecontinuous beam can be scanned to form uniformly the activesemiconductor films of many thin film transistors in a large-sizecrystalline state (flow pattern).

[0030] According to the fourth aspect of the present invention, like thethird aspect, there is provided a semiconductor manufacturing apparatus.The apparatus comprising disposing means for disposing anon-crystallized substrate on a surface of which a semiconductor film isformed, so that the non-crystallized substrate can freely be moved in aplane parallel with a surface of the semiconductor film, laseroscillation means that can output an energy beam continuous in relationto time, and beam splitting means for optically splitting the energybeam emitted from the laser oscillation means, into sub-beams. Each ofthe sub-beams is applied to relatively scan the corresponding portion ofthe semiconductor film to crystallize.

[0031] In this case, with the split sub-beams, the predeterminedportions of the semiconductor film corresponding to the respectivesub-beams can be crystallized at once. Thus, each of the activesemiconductor films of many thin film transistors can be formeduniformly in a large-size crystalline state (flow pattern). Besides,even when using laser oscillation means whose output is lower than thoseof excimer lasers, such as a CW laser, a very high throughput notinferior to those in case of using excimer lasers can be obtained.Crystallization for thin film transistors can efficiently be achievedthereby.

[0032] In the fourth aspect, each sub-beam is preferably controlled sothat only the portion where a thin film transistor is to be formed isirradiated with the beam at the optimum energy intensity forcrystallization and the beam rapidly pass the portion where no thin filmtransistor is to be formed. A higher throughput can be obtained thereby,and very highly efficient crystallization for thin film transistors canbe realized.

[0033] According to the fifth aspect of the present invention, like thethird aspect, there is provided a semiconductor manufacturing apparatus.The apparatus comprising disposing means for disposing anon-crystallized substrate on a surface of which a semiconductor film isformed, so that the non-crystallized substrate can freely be moved in aplane parallel with a surface of the semiconductor film, laseroscillation means that can output an energy beam continuous in relationto time, and intermittent (pulse) emission means having a transmissionarea and an interruption area for the energy beam to intermittentlytransmit the energy beam. With moving the energy beam to relatively scanthe non-crystallized substrate, the energy beam is intermittentlyapplied to the semiconductor film to selectively crystallize only theportion where a thin film transistor is to be formed.

[0034] In this case, by controlling the transmission of the energy beammainly with the intermittent emission means, only desired portions ofthe semiconductor film can be selectively crystallized. That is, onlydesired portions of the semiconductor film in the non-patterned statecan be selectively crystallized. Therefore, it is needless to set up inadvance the portions to be irradiated with the beam, i.e., the portions(ribbon-like or island-like) where thin film transistors are to beformed. As a result, the number of manufacturing steps can be reducedand the throughput can be improved.

[0035] In the fifth aspect, it is preferable that the energy beam isintermittently applied to certain portions other than where thin filmtransistors are to be formed, so as to form positioning markers for thethin film transistors each crystallized into a predetermined shape. Byforming the positioning markers simultaneously with the crystallizationof where thin film transistors are to be formed, the number ofmanufacturing steps can be reduced and efficient and accurate formationof the thin film transistors becomes possible.

[0036] The present invention includes semiconductor devices andmanufacturing methods of the semiconductor devices, corresponding to theabove fourth and fifth aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIGS. 1A and 1B are schematic plan views showing the crystallizingstate of a semiconductor film in the first embodiment of the presentinvention;

[0038]FIGS. 2A and 2B are a plan view and a photomicrographic view,respectively, showing the state of a semiconductor film patterned into aribbon shape;

[0039]FIGS. 3A and 3B are photomicrographic views showing a state inwhich a TFT island is formed;

[0040]FIG. 4 is a SEM view showing the state of a semiconductor filmcrystallized by a CW laser (flow pattern);

[0041]FIG. 5 is a SEM view showing the state of a semiconductor filmcrystallized into an excimer pattern by a CW laser;

[0042]FIG. 6 is a graph showing SIMS analysis around a semiconductorfilm;

[0043]FIG. 7 is a photographic view showing sectional TEM around asemiconductor film;

[0044]FIGS. 8A to 8C are schematic sectional views, respectively,showing the steps in manufacturing a TFT according to the firstembodiment;

[0045]FIGS. 9A to 9C are schematic sectional views, respectively,showing the steps subsequent to FIG. 8C in manufacturing a TFT accordingto the first embodiment;

[0046]FIGS. 10A and 10B are schematic sectional views, respectively,showing the steps subsequent to FIG. 9C in manufacturing a TFT accordingto the first embodiment;

[0047]FIGS. 11A to 11C are schematic sectional views, respectively,showing the steps subsequent to FIG. 10B in manufacturing a TFTaccording to the first embodiment;

[0048]FIG. 12 is a graph showing the relationship between the crystalpattern and mobility of a semiconductor film;

[0049]FIG. 13 is a photomicrographic view showing the relationshipbetween the crystal pattern and mobility of the semiconductor film;

[0050]FIG. 14 is a schematic plan view showing ribbon-shapedsemiconductor films and position markers in the first modification ofthe first embodiment;

[0051]FIGS. 15A to 15D are schematic plan views showing the states of asemiconductor film in the second modification of the first embodiment;

[0052]FIGS. 16A to 16D are schematic views showing the states of asemiconductor film in the third modification of the first embodiment;

[0053]FIG. 17 is a schematic plan view showing the states of asemiconductor film in the fourth modification of the first embodiment;

[0054]FIGS. 18A to 18C are schematic views showing the states of asemiconductor film in the fifth modification of the first embodiment;

[0055]FIG. 19 is a schematic view showing a DPSS laser device in thesecond embodiment of the present invention;

[0056]FIG. 20 is a schematic view showing a DPSS laser device in thefirst modification of the second embodiment;

[0057]FIG. 21 is a schematic view showing a DPSS laser device in thesecond modification of the second embodiment;

[0058]FIG. 22 is a schematic view showing part of a DPSS laser deviceaccording to the third embodiment of the present invention;

[0059]FIG. 23 is a schematic view showing a state that 28 sub-beams intotal are generated using four DPSS lasers;

[0060]FIGS. 24A and 24B are a schematic view showing another irradiationmethod using the DPSS lasers;

[0061]FIG. 25 is a schematic view showing a state of selectivelycrystallizing a semiconductor film only at regions where TFTs are to beformed;

[0062] FIGS. 26 are schematic views showing irradiation systems of DPSSlasers used in modifications of the third embodiment;

[0063]FIG. 27 is a schematic view showing the principal part of a DPSSlaser device according to the fourth embodiment of the presentinvention;

[0064]FIG. 28 is a schematic view showing an example of arrangement ofTFTs in a pixel region;

[0065]FIG. 29 is a schematic view showing the principal part of a DPSSlaser device according to modification 2 of the fourth embodiment;

[0066]FIG. 30 is a schematic view showing the principal part of a DPSSlaser device according to modification 3 of the fourth embodiment;

[0067]FIG. 31 is a schematic view showing the principal part of a DPSSlaser device according to modification 4 of the fourth embodiment;

[0068]FIG. 32 is a graph showing a result obtained by examining thedistribution of hydrogen in a buffer layer made of SiN or SiON, and a Silayer;

[0069]FIG. 33 is a photomicrographic view showing a state of an a-Sifilm peeling off;

[0070]FIG. 34 is a schematic sectional view showing a state that an a-Sifilm is formed over a glass substrate with a buffer layer beinginterposed between them;

[0071]FIG. 35 is a graph showing an result of an SIMS analysis of aglass substrate/SiN/SiO₂/a-Si structure after a thermal treatment at500° C. for two hours;

[0072]FIG. 36 is a photomicrographic view showing a semiconductor filmafter crystallization; and

[0073]FIG. 37 is an AFM view showing a state of a silicon filmcrystallized using a conventional excimer laser.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0074] Preferred embodiments to which the present invention is appliedwill be described below in detail with reference to drawings.

[0075] (First Embodiment)

Crystallization by Energy Beam Output Continuously along Time Axis

[0076] The principal part of the first embodiment of the presentinvention, i.e., crystallization of a semiconductor film using an energybeam which outputs energy continuously along the time axis, e.g., asolid state laser (DPSS (Diode Pumped Solid State Laser) laser) ofsemiconductor excitation (LD excitation) will be disclosed.

[0077] An energy beam continuous along the time axis can irradiate andscan, e.g., an amorphous silicon (a-Si film) to form large-sizepolysilicon crystals. The crystal grain size at this time is aboutseveral μm, and very large crystals can be formed. This crystal grainsize is 10 to 100 times the size obtained by using a currently availableexcimer laser. Hence, such crystals are very advantageous to TFTs at aperipheral circuit portion required to operate at high speed.

[0078] As shown in FIGS. 1A to 2B, an a-Si film 2 is patterned into alinear (ribbon) shape (FIG. 1A) or an island shape (FIG. 1B) on a glasssubstrate 1 having an SiO₂ buffer formed thereon. The upper surface ofthe a-Si film 2 or the lower surface of the glass substrate 1 isirradiated and scanned with an energy beam 3 output continuously alongthe time axis from a CW laser in a direction indicated by an arrow.After this, as shown in FIGS. 3A and 3B, each ribbon-shapedsemiconductor film 2 (FIG. 3A) or each island-shaped semiconductor film2 (FIG. 3B) is patterned and etched to form a TFT island region 6 havingsource and drain regions 5 via a channel region 4 in the semiconductorfilm 2.

[0079] Microcrystals are formed around the island region 6 because thecooling rate is high due to thermal diffusion to the peripheral region.However, the cooling rate in the island region 6 can be set sufficientlylow by properly selecting the irradiation conditions (energy and scanspeed) of the CW laser 3, and crystal grains several μm in width andseveral ten μm in length are formed. Thus, the crystal grain size of thechannel portion can be increased.

[0080] The crystallization technique using an energy beam continuousalong the time axis has conventionally been studied in the SOI (SiliconOn Insulator) field, but a glass substrate has been considered not toresist heat. When a glass substrate is irradiated with a laser while ana-Si film is formed on the entire surface, the temperature of the glasssubstrate rises along with the temperature rise of the a-Si film, anddamage such as cracks is observed. To solve this, the a-Si film isprocessed into a ribbon or island shape in advance to prevent thetemperature rise of the glass substrate, generation of cracks, anddiffusion of impurities into the film.

[0081] To form many TFTs in a large area, the energy beam must bestable. A solid state laser of semiconductor LD excitation has astability of 0.1 rms % noise or less and an energy stability of <±1%/h,and is superior to other energy beams.

[0082] An example of crystallization using a diode pumped solid statelaser (DPSS laser) with semiconductor excitation (LD excitation) will bedescribed below.

[0083] The wavelength of the solid state laser is 532 nm (the secondharmonic of Nd:YVO₄, the second harmonic of Nd:YAG, or the like). Theenergy beam output stability is <0.1 rms % noise, and the output timestability is <±1%/h. Note that the wavelength is not limited to this,and any wavelength capable of crystallizing a semiconductor film may beused. The output is 10 W, and NA35 glass is used as a non-crystallizedsubstrate. The material of the non-crystallized substrate is not limitedto this, and may be another non-alkali glass, silica glass,single-crystal silicon with amorphous insulating layer, ceramics,plastic, or the like.

[0084] An SiO₂ buffer layer is formed at a film thickness of about 400nm between a glass substrate and a semiconductor film. Note that thebuffer layer is not limited to this, and may be a layered structure ofan SiO₂ film and SiN film. The go semiconductor film is a silicon thinfilm formed by plasma CVD. Heat treatment for dehydrogenation is done at450° for 2 h before energy irradiation. Dehydrogenation is not limitedto heat treatment, and may be achieved by emitting an energy beam manytimes while gradually increasing the energy level from a low energyside. In this embodiment, the semiconductor film is irradiated from thelower surface via the glass, but is not limited to this. Thesemiconductor film may be irradiated from the semiconductor film side.

[0085] The energy beam is shaped into an elongated linear beam(rectangular beam) 400 μm×40 μm in size. The size and shape of theenergy beam are not limited to them, and the energy beam may be adjustedto an optimal size necessary for crystallization. As the shape of thebeam, a rectangular (or elliptic) beam, a linear (or elliptic) beam, orthe like, can be suitably used. Although it is preferable that such along linear (or elliptic) beam, rectangular (or elliptic) beam, orlinear (or elliptic) beam has uniform distribution of energy intensityin the beam, it is not always required. Such a beam may have an energyprofile in which the maximum intensity is at the center of the beam.

[0086] In this embodiment, as shown in FIGS. 2A and 2B, the a-Si film 2is patterned into a ribbon shape in the silicon region where a TFT isformed. Adjacent ribbon-shaped a-Si films 2 are separated by apredetermined distance, and a region where no a-Si film 2 exists ispresent. This layout of the a-Si films 2 can greatly reduce thermaldamage to the NA35 glass substrate 1. Note that the a-Si film is notlimited to the ribbon shape, but may be patterned into an island shape.

[0087]FIG. 4 shows the results of crystallizing an a-Si film at anenergy beam scan speed of 20 cm/s.

[0088] Crystals 5 μm or more in crystal grain size are found to beformed. This crystal grain size corresponds to a size 10 to 100 timesthe grain size of crystallization by an excimer laser. Crystal grains asif they flow in a scan direction are observed, and this crystal patternis defined as a “flow pattern” in this embodiment. The name is notlimited to this, and is defined for descriptive convenience in thisembodiment. As a crystal grain size different from that of the flowpattern, a pattern as shown in FIG. 5 similar to a crystallizationpattern by an excimer laser in FIG. 37 is sometimes formed. This crystalgrain pattern is defined as an “excimer pattern” in this embodiment. Theexcimer pattern is formed due to an improper energy density or scanspeed (or both of them).

[0089] The results of observing the influence of a large amount ofimpurities present in glass on a crystallized film will be described.

[0090] In this embodiment, the SiO₂ film about 400 nm in film thicknessformed by PECVD is interposed between the NA35 glass substrate 1 and thea-Si film 2 serving as a semiconductor film. The buffer layer is notlimited to this, and may be 200 nm or more in film thickness for singleSiO₂ or may use a layered structure of SiO₂ film and SiN film.

[0091]FIG. 6 shows the results of SIMS analysis.

[0092] It is confirmed that impurities (aluminum, boron, sodium, andbarium) in glass do not exist in a crystallized semiconductor thin film.Aluminum is observed in data, but is a ghost. Aluminum does not actuallyexist in the film. The density of sodium is lower than detection limit.

[0093]FIG. 7 shows the results of inspecting thermal damage to NA35glass (results of observing sectional TEM).

[0094] As shown in FIG. 7, the interface between the glass and thebuffer layer is definite, and no damage to the glass can be confirmed.

[0095] In this embodiment, crystallization is achieved using one DPSSlaser having an output of 10 W and a wavelength of 532 nm. When thelayout of a semiconductor thin film pattern is already known, as shownin FIGS. 2A and 2B, it is possible to form plural beams andsimultaneously emit them while matching them with semiconductor thinfilm regions. At this time, plural energy beam generators may be used,or an energy beam from one generator may be split into beams.

Fabrication of TFT

[0096] An example of fabrication of an n-channel thin film transistorusing the above-described energy beam output continuously along the timeaxis will be explained. FIGS. 8A to 11C are schematic sectional views,respectively, showing the steps in manufacturing the thin filmtransistor.

[0097] As a non-crystallized substrate, an NA35 glass substrate 21 isused similarly to the above example. As shown in FIG. 8A, an SiO₂ bufferlayer 22 about 400 nm in film thickness, and a patterning Si thin filmhaving a non-crystallized silicon thin film are formed on the glasssubstrate 21. Heat treatment is done at 450° for 2 h for the sake ofdehydrogenation. Dehydrogenation is not limited to heat treatment, andmay be achieved by emitting an energy beam many times while graduallyincreasing the energy level from a low energy side.

[0098] Then, the a-Si film 2 is crystallized using the above-mentionedenergy beam output continuously along the time axis, thereby forming anactive semiconductor film 11.

[0099] More specifically, as shown in, e.g., FIG. 2A, a semiconductorfilm, in this case the a-Si film 2 is formed in a ribbon shape. A DPSSlaser is used with a wavelength of 532 nm, an energy beam stability of<0.1 rms % noise and an output stability of ±1%/h. The a-Si film 2 iscrystallized by irradiating and scanning it by a linear beam 400 μm×40μm in energy beam size at a scan speed of 20 cm/s.

[0100] Subsequently, as shown in, e.g., FIG. 3A, a TFT island region 6is formed in the crystallized ribbon-shaped semiconductor film. At thistime, the semiconductor film is so processed as to position a TFTchannel region 4 on the central axis of the ribbon-shaped semiconductorfilm. That is, a current flowing in a completed TFT coincides with thelaser beam scan direction. In this case, as shown in the lower part ofFIG. 2A, a plurality (three in the illustrated example) of TFTs may beformed in each ribbon width.

[0101] As shown in FIG. 8B, a silicon oxide film 23 serving as a gateoxide film is formed to a film thickness of about 200 nm on the activesemiconductor film 11 by PECVD. The silicon oxide film 23 may be formedby another method such as LPCVD or sputtering.

[0102] As shown in FIG. 8C, an aluminum film (or aluminum alloy film) 24is sputtered to a film thickness of about 300 nm.

[0103] As shown in FIG. 9A, the aluminum film 24 is patterned into anelectrode shape by photolithography and dry etching, thereby forming agate electrode 24.

[0104] As shown in FIG. 9B, the silicon oxide film 23 is patterned usingthe patterned gate electrode 24 as a mask, thereby forming a gate oxidefilm 23 conforming to the gate electrode shape.

[0105] As shown in FIG. 9C, ions are implanted in the two sides of thegate electrode 24 of the active semiconductor film 11 using the gateelectrode 24 as a mask. More specifically, n-type impurities, in thiscase phosphorus (P) are ion-implanted at an acceleration energy of 20keV and a dose of 4×10¹⁵/cm², thereby forming source and drain regions.

[0106] As shown in FIG. 10A, the resultant structure is irradiated withan excimer laser in order to activate phosphorous in the source anddrain regions. Then, as shown in FIG. 10B, SiN is deposited to a filmthickness of about 300 nm so as to cover the entire surface, therebyforming an interlevel insulating film 25.

[0107] As shown in FIG. 11A, contact holes 26 for exposing the gateelectrode 24 and the source and drain regions of the activesemiconductor film 11 are formed in the interlevel insulating film 25.

[0108] As shown in FIG. 11B, metal films 27 of aluminum or the like areformed to bury the contact holes 26. As shown in FIG. 11C, the metalfilms 27 are patterned to form wiring lines 27 which connect the gateelectrode 24 and the source and drain regions of the activesemiconductor film 11 via the contact holes 26. After that, formation ofa protection film which covers the entire surface, and the like areperformed to complete the n-type TFT.

[0109] The relationship between TFT characteristics and the crystalquality was checked using the n-channel TFT fabricated by the abovesteps. FIG. 12 shows experimental results.

[0110] When the crystal pattern of the channel region is a flow pattern,the mobility is higher than that in an excimer laser pattern. Thehighest mobility is 470 cm²/Vs. The mobility is strongly related to theflow pattern shape. As shown in FIG. 13, the mobility is confirmed to behigher in a strong flow pattern shape than in a weak flow pattern shape.

[0111] As described above, this embodiment can implement TFTs in whichthe transistor characteristics of the TFTs are made uniform at highlevel, and the mobility is high particularly in a peripheral circuitregion to enable high-speed driving. This can implement ahigh-performance, peripheral circuit-integrated TFT-LCD, system-onpanel, or system-on glass having many TFTs.

Modifications

[0112] Modifications of the first embodiment will be described.

[0113] (First Modification)

[0114]FIG. 14 is a schematic plan view showing a state on a glasssubstrate in the first modification.

[0115] In this modification, the ribbon-shaped a-Si films 2 are formedas semiconductor films on the glass substrate 1, and a position marker31 is set at an end portion of the glass substrate 1 corresponding toeach a-Si film 2. Although the a-Si films are ribbon-shaped in theillustrated example, they may alternatively be island-shaped.

[0116] In irradiating and scanning the a-Si film 2 with an energy beamfrom the CW laser 3, the irradiation position can be automaticallysearched with reference to the position marker 31. After the irradiationposition is determined, the energy beam is scanned to performcrystallization.

[0117] This modification can suppress a shift in the irradiationposition of the energy beam. Supply of a stable continuous beam enablesso-called lateral growth, and an active semiconductor film havinglarge-size crystal grains can be reliably formed.

[0118] (Second Modification)

[0119]FIGS. 15A to 15D are schematic plan views for explaining thesecond modification.

[0120] As shown in FIG. 15A, the a-Si film is processed into an islandshape having two almost parallel slits 32 and an island region isformed.

[0121] The upper surface of the a-Si film is irradiated with a CW laser,e.g., Nd:YVO₄ laser (2ω, wavelength of 532 nm) in the direction of theslit 32 (indicated by an arrow) at an energy of 6 W, a beam size of 400μm×40 μm, and a scan speed of 20 cm/s. Even irradiation from the uppersurface can normally crystallize the a-Si film. If the a-Si film isirradiated from the lower surface, the sample holder is also heated toobtain a heat-insulating effect on the film surface side and easilyobtain higher-quality crystals. The a-Si film is fused and crystallized.The cooling rate is high around the island region 6 owing to thermaldiffusion to the peripheral region, so that microcrystals are formed. Inthe channel region 4, the cooling rate can be set sufficiently low byproperly selecting the irradiation conditions (energy and scan speed) ofthe CW laser, and crystal grains several μm in width and several ten μmin length are formed.

[0122] At this time, as shown in FIG. 15B, the slits 32 block crystalgrains and grain boundaries which grow inward from the periphery and areto cross the channel region. Only crystal grains which grow parallel tothe slits 32 are formed between the slits 32. If the interval betweenthe slits 32 is satisfactorily small, this region is formed from singlecrystals. The slit width of each slit 32 is preferably formed as smallas possible so as not to change the region between the slits 32 intomicrocrystals, while the slit 32 holding the grain boundary blockingeffect. The interval between the slits 32 is set with a margin inaccordance with the channel width of the device.

[0123] As shown in FIG. 15C, the resultant structure is patterned by dryetching so as to set the single-crystal portion between the slits 32 asthe channel region 4, thereby completing the TFT.

[0124] As shown in FIG. 15D, a gate insulating film and gate electrodeare formed by a known method. After impurities are implanted andactivated, a source and drain are formed to fabricate the TFT.

[0125] By crystallization using this method, single crystals can beselectively obtained at a necessary portion of the channel region of theTFT. In a TFT formed using an active semiconductor film prepared in thisway, only one crystal grain exists in the channel region. Thus, thecharacteristics are improved, and variations caused by crystallinity andthe crystal grain boundary are greatly reduced. Further, variousprocesses on a glass substrate can be performed, and a high-performancedisplay with high value added at low cost can be provided.

[0126] (Third Modification)

[0127]FIGS. 16A to 16D are schematic plan views for explaining the thirdmodification, and schematic sectional views taken along the line I-I′.

[0128] After the SiO₂ underlayer and a-Si film 2 are successively formedon the glass substrate 1, the a-Si film 2 is patterned into an islandshape, as shown in FIG. 16A.

[0129] As shown in FIG. 16B, an SiO₂ film is formed to a film thicknessof about 50 nm on the a-Si film 2 by CVD or the like, and processed intotwo parallel thin-line patterns 33.

[0130] As shown in FIG. 16C, the a-Si film 2 is irradiated and scannedwith a CW laser from the upper surface. The irradiation conditions arethe same as in the first embodiment. At this time, the a-Si film 2 isfused and crystallized again by laser heating. However, since thethin-line patterns 33 exist on the a-Si film 2, fused Si easily gathersby the surface tension, and Si thin lines 33 a independent of theperiphery are formed at the lower portions of the thin-line patterns 33.The Si thin lines block crystal grains and crystal grain boundarieswhich are to cross the channel. As a result, only crystal grains whichgrow parallel to the thin lines are formed between the two thin-linepatterns 33.

[0131] The SiO₂ films of the thin-line patterns 33 are removed with anaqueous HF solution or the like. As shown in FIG. 16D, the resultantstructure is processed by dry etching so as to set the single-crystalportion between the thin-line patterns 33 as the channel region 4.Thereafter, a gate insulating film and gate electrode are formed by aknown method, thereby fabricating the TFT.

[0132] By crystallization using this method, single crystals can beselectively obtained at a necessary portion of the channel region of theTFT. In a TFT formed using an active semiconductor film prepared in thismanner, only one crystal grain exists in the channel region. Thecharacteristics are improved, and variations caused by crystallinity andthe crystal grain boundary are greatly reduced. Moreover, variousprocesses on a glass substrate can be performed, and a high-performancedisplay with high value added at low cost can be provided.

[0133] (Fourth Modification)

[0134] The fourth modification is almost the same in the manufacturingprocess as the second modification except for the slit shape. FIG. 17shows a slit shape in the fourth modification. Unlike the slit shape inFIGS. 15A to 15C, two slits 32 are not completely parallel, but areslightly widened in the laser scan direction. This shape can moreefficiently block crystal grain boundaries diagonally inward from theperiphery. In addition, crystal grains extending from the lower side inthe drawing can be easily selected by the necking effect. The subsequentprocess is the same as in the second modification.

[0135] (Fifth Modification)

[0136]FIGS. 18A to 18C are schematic views for explaining the fifthmodification. The upper portion of FIG. 18A is a plan view of apatterning portion, and the lower portion is a sectional view takenalong the line I-I′. FIGS. 18B and 18C show manufacturing stepssubsequent to FIG. 18A.

[0137] In an a-Si film 2, a thin film region 34 is surrounded by athick-film region 35. Scanning and irradiation with a CW laser areexecuted in the longitudinal direction of the thin film region 34 (seeFIG. 18A). At this time, the thick-film region 35 has a large heatcapacity due to its thickness, and decreases in cooling rate duringsolidification. Hence, the thick-film region 35 has a hot bath effect onthe thin film region 34. In the thin film region 34, the crystal grainboundary spreads toward the peripheral thick-film region 35 (see FIG.18B). This means that the defect (crystal grain boundary) densitydecreases in the thin film region 34. That is, high-quality crystals canbe implemented.

[0138] By using the thin film region 34 as the channel region of theTFT, a high-performance TFT can be implemented (see FIG. 18C).

[0139] (Second Embodiment)

[0140] The second embodiment of the present invention will be describedbelow.

[0141] The construction of the DPSS laser device used in the firstembodiment will be explained.

[0142]FIG. 19 is a view showing the outer appearance of the wholeconstruction of a DPSS laser device according to the second embodiment.

[0143] This DPSS laser device comprises a DPSS laser 41 of solidsemiconductor LD excitation, an optical system 42 for irradiating apredetermined position with a laser beam emitted by the DPSS laser 41,and an X-Y stage 43 freely drivable in horizontal and verticaldirections to which a glass substrate to be irradiated is fixed.

[0144] In the second embodiment, the glass substrate is made of NA35glass (non-alkali glass), and the laser wavelength is 532 nm. Outputvariations in energy beam are noise of 0.1 rms % or less, the outputinstability is <±1%/h, and the output of the energy beam is 10 W. Notethat the wavelength is not limited to this value, and any wavelengthcapable of crystallizing a silicon film may be used. Also, the beamoutput is not limited to this value, and a device having an appropriateoutput may be used.

[0145] The energy beam is shaped into a linear beam (rectangular beam)400 μm×40 μm in size. The size and shape of the energy beam are notlimited to them, and the energy beam may be adjusted to an optimal sizenecessary for crystallization. Energy variations in the longitudinaldirection are within 40% using the center as the maximum intensity.

[0146] The glass substrate is set on the X-Y stage 43 to beperpendicular to the optical axis.

[0147] In the second embodiment, as well as the first embodiment, asemiconductor film (a-Si film) on which a TFT is to be fabricated isformed into a ribbon or island shape, as shown in FIG. 1A or 1B.Adjacent a-Si films are separated, and a region where no a-Si filmexists is present. This reduces thermal damage to the glass substrateemployed in this embodiment.

[0148] The energy beam scan speed is 20 cm/s. This embodiment adopts themotor-driven X-Y stage 43. Note that the driving mechanism of the X-Ystage 43 is not limited to this, and another stage can be used as far asit can be driven at a speed of 15 cm/s or more. Scanning with the energybeam can be performed by moving the energy beam relatively to the X-Ystage 43. That is, either the energy beam or the X-Y stage can be moved.

[0149] When polysilicon is to be formed on the glass substrate,positional control during scan is important because the currentsubstrate size is 400 mm×500 mm. The X-Y stage 43 of this embodimentexhibits a positional variation of 10 μm or less every one-metermovement.

[0150] The DPSS laser device of this embodiment can supply a stablecontinuous beam by setting the energy beam output instability to a valuesmaller than ±1%, and preferably setting noise representing the energybeam instability with respect to the time to 0.1 rms % or less. Byscanning this continuous beam, the active semiconductor films of manyTFTs can be uniformly formed in a crystalline state (flow pattern)having a large grain size.

Modifications

[0151] Modifications of the second embodiment will be described below.

[0152] (First Modification)

[0153]FIG. 20 shows the whole construction of a DPSS laser deviceaccording to the first modification.

[0154] This modification uses the two DPSS lasers 41 having an outputstability of 0.1 rms % noise or less, an output instability of <±1%/h,and an output of 10 W. Laser beams emitted by the two DPSS lasers 41 aremultiplexed into one midway along the optical path, thereby improvingthe output.

[0155] The beam size is set to 800 μm×40 μm so as to irradiate a largerarea than in the second embodiment. Similar to the first embodiment,this modification has a function of reading and irradiating a positionmarker.

[0156] The X-Y stage 43 is horizontally placed, and a glass substrate ishorizontally set. A magnetic levitation type moving mechanism isdisposed in the irradiation/scan direction, whereas a normal motordriving scheme is used in the X-axis direction. The energy beam isvertically emitted.

[0157] In addition to the effects of the second embodiment, the DPSSlaser device of the first modification can supply a stabler continuousbeam by providing DPSS lasers 41 (two in this case). By scanning thiscontinuous beam, the active semiconductor films of many TFTs can beuniformly formed in a crystalline state (flow pattern) having a largegrain size.

[0158] (Second Modification)

[0159]FIG. 21 shows the whole construction of a DPSS laser deviceaccording to the second modification.

[0160] This modification adopts the two DPSS lasers 41 having the sameoutput stability, output, and the like as in the first modification, andirradiates different locations. Each energy beam has a function ofreading an irradiation position from a position marker.

[0161] In addition to the effects of the second embodiment, the DPSSlaser device of the second modification can rapidly supply a stablercontinuous beam by providing DPSS lasers 41 (two in this case). Byscanning this continuous beam, the active semiconductor films of manyTFTs can be uniformly formed in a crystalline state (flow pattern)having a large grain size.

[0162] (Third Embodiment)

[0163] Next, the third embodiment of the present invention will bedescribed.

[0164] Here, like the second embodiment, the construction of a DPSSlaser device and then a crystallization method of a semiconductor filmusing the DPSS laser device will be described. The DPSS laser device ofthis embodiment differs from that of the second embodiment on the pointthat the energy beam is split as described below.

[0165] In this embodiment described is an example of crystallization inthe pixel region using a semiconductor exciting (LD exciting) solidstate laser (DPSS laser) Nd:YVO₄. In this embodiment, a crystallizationtechnique for the pixel region will be described, but the presentinvention is not limited to this. The present invention is applicablealso to crystallization for any peripheral circuit. The laser is notlimited to Nd:YVO₄. A similar DPSS laser light (e.g., Nd:YAG or thelike) can be used also. The wavelength is 532 nm. The wavelength is notlimited to this. Any wavelength can be used if it can melt silicon. Thestability of the energy output is <0.1 rms % of noise, the stability oftime of the output is <±1%/h, and the output is 10 W.

[0166] As the non-crystallized substrate used is an NA35 glasssubstrate. The non-crystallized substrate is not limited to this.Another non-alkali glass, quartz glass, monocrystalline substrate withamorphous insulating layer, ceramic, or plastic can be used.

[0167] An about 400 nm-thick buffer layer made of SiO₂ is formed betweenthe glass substrate and a semiconductor film. The buffer layer is notlimited to this. It can be a multilayer film of SiO₂ and SiN. Thesemiconductor film is an about 150 nm-thick silicon film formed througha plasma CVD process. Before irradiation with an energy beam, a thermaltreatment for dehydrogenation has been performed at 500° C. for twohours. Dehydrogenation is not limited to such a thermal treatment. Itcan be implemented by many times of irradiation with an energy beam asthe energy of the beam is gradually increased from the lower energyside. In this embodiment, the irradiation is done from the semiconductorfilm side, but it may be done from the back surface side through theglass.

Construction of DPSS Laser Device

[0168]FIG. 22 is a schematic view showing part of a DPSS laser deviceaccording to this third embodiment.

[0169] The DPSS laser device includes a solid statesemiconductor-exciting DPSS laser 41 (not shown) like the secondembodiment, a diffraction grating 51 as beam splitting means foroptically splitting an energy beam emitted from the DPSS laser 41, intoa number of sub-beams, in the illustrated example, seven sub-beams, acollimator lens 52, a condenser lens 53 for condensing the splitsub-beams, and an X-Y stage 43 (not shown), like the second embodiment,on which the glass substrate to be irradiated is mounted and which canfreely be driven horizontally and vertically.

[0170] Although the diffraction grating 51 is used as the beam splittingmeans in this embodiment, the beam splitting means is not limited tothis. For example, also usable is a polygon mirror, a movable mirror, anAO device (Acousto-Optic Device) using an acoustooptic effect, or an EOdevice (Electro-Optic Device) using an electrooptic effect.

[0171] Each sub-beam has a size of 80 μm×20 μm, which is sufficient forforming a thin film transistor in the pixel region. Each sub-beam has anelliptic beam shape in which the maximum intensity is at the centroid.The beam shape is not limited to such an elliptic beam shape. A longlinear beam (or a rectangular beam) can be used also. The size of theenergy beam is also not limited to the above. Any beam size can be usedif it can form a pixel TFT.

[0172] In this embodiment, each silicon region where a pixel TFT is tobe formed is ribbon-shaped as shown in FIG. 23. Each semiconductor filmribbon 54 is separated from the neighboring semiconductor film ribbon 54on either side, and there is interposed a region including nosemiconductor film portion. This is for reducing thermal damage on theNA35 glass substrate used in this embodiment.

[0173] The pattern of the semiconductor film is not limited to such aribbon shape. An island pattern can be used also. Since such a pixel TFTrequires not so high performance, the beam energy density forcrystallization can be reduced in comparison with the peripheral region.For this reason, even if the amorphous silicon were formed on the entiresurface, crystallization can be performed without damaging the glasssubstrate.

[0174]FIG. 23 is a schematic view showing a state that 28 sub-beams intotal are generated using four DPSS lasers.

[0175] In the crystallization technique for pixel TFTs in thisembodiment, the scanning speed with the energy beam is 100 cm/sec. Thescanning speed is not limited to this value. Any scanning speed can beused if it can implement the required performance of the pixel TFTs.

[0176] In order to irradiate the entire surface of the pixel region, the28 sub-beams in the lump are moved in parallel to crystallize every 28lines. The entire surface of the pixel region is thus crystallized withan improved throughput. In this embodiment, this operation is performedby rapidly moving the X-Y stage 43. But, the present invention is notlimited to this manner. The 28 sub-beams can be moved in the lump whilethe X-Y stage 43 is fixed. The number of sub-beams is 28 in thisembodiment. But, it is of course that the number of sub-beams is notlimited to this value.

[0177] The irradiation method with the beams is not limited to that inFIG. 23. An irradiation method as shown in FIG. 24A is also suitable. Inthis example, a plurality (two in the illustrated example) of lasers areeach divided into a plurality (three in the illustrated example) ofsub-beams. These sub-beams are moved to scan without overlapping eachother. In this example, lateral movement in each scanning operation canbe made shorter in distance.

[0178] Further, for example, an irradiation method as shown in FIG. 24Bcan be suitably used also. In this example, each DPSS laser 41 emits oneenergy beam. The energy beams emitted from the respective DPSS lasers 41are moved without overlapping each other. This irradiation method iseffective particularly for peripheral circuits, which requirecrystallization by a higher energy. This irradiation method is, ofcourse, usable for the pixel region.

[0179] As a result of observing crystal grains in each beam line formedby the method of FIG. 23, it was confirmed that polysilicon with itscrystal grain size of 300 nm was formed.

Fabrication of TFT

[0180] TFTs were fabricated using, as the active semiconductor film, asemiconductor film crystallized with the DPSS laser device of thisembodiment. The fabrication process of the TFTs was the same as that inthe first embodiment described with reference to FIGS. 8 to 11.

[0181] In this embodiment, the semiconductor film to be crystallized wasformed into a ribbon pattern in which 50 μm-wide ribbons were arrangedat certain intervals so as to match the pixel layout. The wavelength was532 nm. The output was 10 W. The stability of the energy beam was <0.1rms % of noise. The stability of the output was <±1%/h. The shape of theenergy beam was elliptic of 80 μm×20 μm. The scanning speed was 100cm/sec. Crystallization was performed under the above conditions.

[0182] When the mobility of a TFT fabricated through the same process asthat in the first embodiment described with reference to FIGS. 8 to 11was examined, it was about 20 cm²/Vs. This value shows a performancethat can be sufficiently put in practical use as a pixel transistor.

Modifications

[0183] Modifications of this third embodiment will be described below.

[0184] Here will be described, as shown in FIG. 25, efficientcrystallization methods for selectively crystallizing the semiconductorfilm only at the regions where TFTs are to be formed.

[0185] FIGS. 26 are schematic views of irradiation systems of DPSS laserdevices used in modifications of this embodiment.

[0186] Referring to FIG. 26A, an irradiation system A is made up from afixed mirror 61 for reflecting a sub-beam in a predetermined direction,and a movable mirror 62 for further reflecting the beam, which has beenreflected by the fixed mirror 61, in a predetermined direction toirradiate the target region. Such an irradiation system A is providedfor each of split sub-beams.

[0187] Referring to FIG. 26B, an irradiation system B is made up from afixed mirror 63 for reflecting a sub-beam to a predetermined direction,a collimator lens 64, and a condenser lens 65 for condensing the beam,which has been reflected by the fixed mirror 63, through the collimatorlens 64 to irradiate the target region. Such an irradiation system B isprovided for each of split sub-beams.

[0188] In addition to moving the X-Y stage 43, the optical system shownin FIG. 26A or 26B is equipped for each of the split sub-beams. Eitheroptical system is designed to scan only the region for forming each TFT.That is, the range of each sub-beam shifting is less than 100 μm atmost.

[0189] While the X-Y stage 43 is rapidly moved, the optical system isturned on at each pixel position to crystallize the pixel portion. Thisbrings about an improvement of the throughput.

[0190] In this embodiment, the amorphous silicon can be formed on theentire surface of the substrate, or into a ribbon or island pattern. Inany case, it is of course that the portions to be irradiated with thelaser beam must be match the layout of the pixel region.

[0191] (Fourth Embodiment)

[0192] Next, the fourth embodiment of the present invention will bedescribed.

[0193] Here, like the second embodiment, the construction of a DPSSlaser device and then a crystallization method of a semiconductor filmusing the DPSS laser device will be described. The DPSS laser device ofthis embodiment differs from that of the second embodiment on the pointthat the laser beam can be selectively applied to arbitrary portions asdescribed below.

[0194] In this embodiment, the a-Si film is not processed in advanceinto an island pattern but it is left as in the non-patterned state. Inthis state, using an energy beam whose size is restricted tosubstantially correspond to the width of each island (about 100 μm orless), irradiation is intermittently carried out while the X-Y stage ismoved. Thus obtained are crystallized regions (molten regions)equivalent to the respective islands in the first embodiment. In thismanner, the problems of damaging the glass substrate and peeling off thefilm can be avoided.

[0195] In case of application to LCDs, while the peripheral circuitregion is highly integrated and it requires TFTs with bettercrystallization and higher mobility, the pixel region includes the areasfor the respective TFTs at relatively large intervals and each TFTrequires not so high mobility. But, the occupied area by the pixelregion is far greater than that by the peripheral circuit region. So, inthe pixel region, the X-Y stage is moved at a high speed (about severalm/s) and crystallization is discretely performed only at necessaryportions, thereby considerably improving the throughput.

Construction of DPSS Laser Device

[0196]FIG. 27 is a schematic view showing the principal part of a DPSSlaser device according to this fourth embodiment.

[0197] The DPSS laser device includes a solid state semiconductor LDexciting laser 41 like the second embodiment, an optical system 71having the function of a collimator and the function of a condenser, achopper 72 as intermittent emission means that is disposed in theoptical path through which the energy beam reaches the a-Si film 70 onthe glass substrate, has transmission (ON) areas 72 a and interruption(OFF) areas 72 b for the energy beam, and can be rotated in the arrowdirection to allow the energy beam to intermittently pass through, amirror 73 for reflecting the energy beam having passed through an ONarea 72 a, to the glass substrate, and an X-Y stage 43 (not shown), likethe second embodiment, that can be freely driven horizontally andvertically. Using this DPSS laser device, a CW laser light, e.g., Nd:YAGlaser light (2ω, the wavelength: 532 nm) is shaped into a beam size of20 μm×5 μm through the optical system 72.

[0198] In this case, it is efficient to scan in the arrow directionindicated in FIG. 28. This is effective even to intermittent irradiationas the case in FIG. 1, for example, not limited to intermittentirradiation with the energy beam.

[0199]FIG. 28 is a schematic view showing an example of arrangement ofTFTs in the pixel region.

[0200] In this embodiment, each pixel size is 150 μm×50 μm and the TFTregion may has a size of 10 μm×15 μm. After a SiO₂ buffer layer(thickness: 200 nm) and then an a-Si film (thickness: 150 nm) are formedon a glass substrate, the chopper 72 is rotated. The energy beam isthereby made ON/OFF at a rate of 7.5 μs/17.5 μs, and applied with ascanning speed (speed of the X-Y stage) of 2 m/sec. In this manner,without processing the a-Si film into an island pattern, withoutdamaging the glass substrate and peeling off the film, only necessaryportions of the a-Si film (e.g., crystallization regions 74 in FIG. 27)can be selectively crystallized.

[0201] Preferably in this case, the energy beam is intermittentlyapplied to certain portions of the a-Si film other than where TFTs areto be formed, to crystallize and form positioning markers 75 (FIG. 27)having a predetermined shape, and these markers 75 (FIG. 27) are used asindexes upon crystallization of the a-Si film.

[0202] When crystallization of the a-Si film is performed by the abovemethod, large-grain crystals can be obtained using the CW laser, andthis does not bring about any increase in process steps and time. In aTFT formed with such a large-grain crystal, the characteristics isimproved and unevenness due to crystal is reduced. Thus, ahigh-performance liquid crystal display device with values added can beprovided with holding down the cost.

Modifications

[0203] Modifications of this fourth embodiment will be described below.

[0204] (Modification 1)

[0205] In this modification, a crystallizing method of the a-Si film forTFTs in the peripheral circuit region of a liquid crystal display devicewill be described.

[0206] In the peripheral circuit region, the degree of integration ishigher than that in the pixel region, and requirement forcrystallization is severe. As regions where TFTs are to be formed,crystallization regions each having a size of 50 μm×200 μm are formed atintervals of 5 μm. A circuit is formed in each of the crystallizationregions. For this purpose, a CW laser is shaped into a beam size of 50μm×5 μm through the optical system. After a SiO₂ buffer layer(thickness: 200 nm) and then an a-Si film (thickness: 150 nm) are formedon a glass substrate, the chopper 72 is rotated. The energy beam isthereby made ON/OFF at a rate of 1 ms/0.025 ms, and applied with ascanning speed (speed of the X-Y stage) of 20 cm/sec. By reducing thescanning speed to about 20 cm/sec, fluent long crystal grains (flowpattern) can be obtained, thereby forming a TFT with a high mobility. Inthis manner, without processing the a-Si film into an island pattern,without damaging the glass substrate and peeling off the film,high-quality crystals can be formed at necessary portions.

[0207] (Modification 2)

[0208] In this modification, the intermittent emission means for makingthe energy beam ON/OFF is implemented by a combination of a small holeand a mirror.

[0209]FIG. 29 is a schematic view showing the principal part of a DPSSlaser device according to this modification 2.

[0210] In addition to the DPSS laser 41 and the optical system 71, theDPSS laser device includes a rotatable mirror for reflecting the energybeam in a desired direction, in place of the chopper 72. The DPSS laserdevice further includes an interruption board 76 having a small hole 76a for allowing only the energy beam in a desired direction to pass. Inthis modification, the mirror 77 is rotated to swing the energy beam.The energy beam is made ON only when it passes the hole 76 a. As themeans for swing the energy beam, a rotatable polygon mirror can also beused.

[0211] (Modification 3)

[0212]FIG. 30 is a schematic view showing the principal part of a DPSSlaser device according to this modification 3.

[0213] The DPSS laser device of this modification has almost the sameconstruction as that in the third embodiment, but differs on the pointthat the chopper 72 is processed and, attendant upon this, a number ofmirrors are disposed.

[0214] In this modification, predetermined ones of the ON areas 72 a ofthe chopper 72 are stopped with interruption plates 81 that can reflectthe energy beam. A number of mirrors 82 are provided for reflecting theenergy beam reflected on the respective interruption plates 81, inpredetermined directions. By this structure, the energy beam reflectedon an interruption plate 81 is turned to irradiate a neighboring line ofthe a-Si film 70 and further the next neighboring line. In case of apixel size of 50 μm×150 μm and a TFT region size of 15 μm×10 μm as shownin FIG. 28, about two-thirds of one scanning period is in the OFF state.By irradiating the neighboring two lines during this OFF period, threelines can be irradiated for every scanning period. Thus, the processtime can be shortened to about one-third.

[0215] During one scanning period with the X-Y stage 43, thenon-irradiation time is several times longer than the irradiation time,so the energy beam is rapidly moved to the neighboring line one afteranother during the non-irradiation time. The idle time can be reducedthereby and the throughput can be improved.

[0216] As described above, according to this modification, byrestricting the energy beam of the CW laser to 100 μm or less andapplying it intermittently, a large-grain crystal can be formed withoutdamaging the glass substrate and peeling off the film. Besides, byirradiating the neighboring lines during the non-irradiation time of oneline, the several lines can be crystallized during every scanningperiod, thereby improving the throughput. This makes it possible tosuppress unevenness of the TFT characteristics dependent upon crystalgrain boundaries or size, and good element characteristics can beobtained. As a result, a high-quality liquid crystal display device withits drive circuit being incorporated therein can be provided.

[0217] (Modification 4)

[0218]FIG. 31 is a schematic view showing the principal part of a DPSSlaser device according to this modification 4.

[0219] The DPSS laser device of this modification has almost the sameconstruction as that in modification 3, but differs on the point that apolygon mirror is used in place of the chopper 72.

[0220] In addition to the DPSS laser 41 and the optical system 71, theDPSS laser device of this modification includes a polygon mirror 83 inplace of the chopper 72, and an interruption board 84 having a number of(in the illustrated example, three) holes 84 a for allowing only theenergy beams in predetermined directions to pass, in accordance with thedirections of the energy beam reflected on the polygon mirror 83.

[0221] In this modification, the polygon mirror 83 is rotated to swingthe energy beam, and thereby three lines on the a-Si film 70 areirradiated at once during one scanning period. But, after the first lineis irradiated, since the X-Y stage 43 has moved, the irradiation portionof the second line (the position of the hole 84 a) must be located atthe position advanced in accordance with the movement of the X-Y stage43. The same applies also to the third line.

[0222] According to this modification, like modification 3, alarge-grain crystal can be formed without damaging the glass substrateand peeling off the film. Besides, by irradiating the neighboring linesduring the non-irradiation time of one line, the several lines can becrystallized during every scanning period, thereby improving thethroughput.

[0223] On the fourth embodiment and its modifications 1 to 4, as shownin FIG. 27 to FIG. 31, the energy beam is scanning the X-Y stage to bemoved in the bold arrow direction. When one line is scanned, the energybeam is moved in the narrow arrow direction to scan next line.

[0224] (Fifth Embodiment)

[0225] Next, the fifth embodiment of the present invention will bedescribed.

[0226] In this embodiment, for making TFTs, an a-Si film is crystallizedwith a CW laser, like the first to fourth embodiments. At this time,this embodiment is aimed principally at preventing peeling-off of thea-Si film, which is caused by the temperature rising of a buffer layerdue to irradiation with the energy beam. This embodiment discloses TFTswith a proper buffer layer.

[0227] It is known that the use of SiN or SiON as the material of thebuffer layer formed between the glass substrate and the a-Si film iseffective for preventing contamination by impurities such as sodium fromthe glass constituting the substrate. FIG. 32 shows a result obtained byexamining the distribution of hydrogen in a buffer layer that is notmodified after it is formed.

[0228] When an a-Si film formed over a substrate with a buffer layerbeing interposed between them, which layer contains SiN or SiON, iscrystallized with an energy beam that generates energy continuously inrelation to time, in this example, a CW laser, because the buffer layerabsorbs the energy beam (or due to thermal conduction when the a-Si filmis melted), the temperature rises. When the density of hydrogen in thebuffer layer is high, effusion of hydrogen atoms occurs to generatepinholes, which causes peeling-off of the film. Also, when the densityof hydrogen in the a-Si film is high, effusion occurs to generatepinholes. When both the densities are high, as shown in FIG. 33, thea-Si film is peeled off due to pinholes. This phenomenon is remarkableparticularly when using a continuous energy beam, in comparison with thecrystallization using a conventional excimer laser.

[0229] So, in this embodiment, as shown in FIG. 34, an a-Si film 93 isformed over a glass substrate 91 with a buffer layer 92 being interposedbetween them. The buffer layer 92 is a multilayer film made up from athin SiN or SION film 92 a having a thickness of about 40 nm and a SiO₂film 92 b. Prior to crystallization of the a-Si film 93 with a CW laser,the density of hydrogen in either of the a-Si film 93 and the thin film92 a is regulated. More specifically, the density of hydrogen in thea-Si film 93 is regulated to 1×10²⁰/cm³ or less, and the density ofhydrogen in the thin film 92 a is regulated to 1×10²²/cm³ or less. Byproviding the SiO₂ film 92 b, interface state density between Si filmand buffer layer can be reduced. Besides, upon irradiation with theenergy beam of the CW laser, irradiation from the upper surface side ofthe substrate is preferable to irradiation from the lower surface sideof the substrate because SiN is not directly irradiated with the laserlight.

[0230] [Proper Density of Hydrogen in a-Si Film]

[0231] Here will be described an experimental result obtained byexamining the proper density of hydrogen in the a-Si film.

[0232] As shown in FIG. 34, a thin SiN film 92 a having a thickness ofabout 50 nm and then a SiO₂ film 92 b having a thickness of about 200 nmwere formed on a glass substrate 91 through a P-CVD process to form abuffer layer 92. An a-Si film 93 having a thickness of about 150 nm wasthen formed thereon. The thickness of each film is not limited to theabove value.

[0233] Subsequently, the a-Si film 93 was dehydrogenated by a thermaltreatment in a nitrogen atmosphere at 500° C. for two hours. After this,crystallization was performed with a semiconductor-exciting(LD-exciting) solid state laser (DPSS laser) Nd:YVO₄ under conditions ofan output of 6.5 W, a scanning speed of 20 cm/sec, and a wavelength of532 nm (the second harmonic of Nd:YVO₄). Scanning was performed bymoving the X-Y stage.

[0234]FIG. 35 is a graph showing an result of an SIMS analysis of theglass substrate/SiN/SiO₂/a-Si structure after the thermal treatment at500° C. for two hours.

[0235] In this SIMS analysis, after the thermal treatment at 500° C. fortwo hours, it was confirmed that the density of hydrogen in the a-Sifilm 93 became 1×10²⁰/cm³ or less.

[0236]FIG. 36 is a photomicrographic view showing the semiconductor filmafter crystallization.

[0237] It is found that a good crystal without pinholes and peeling-offcould be obtained by regulating the density of hydrogen in the a-Si film93 to 1×10²⁰/cm³ or less.

[0238] [Proper Density of Hydrogen in SiN Film]

[0239] Next will be described an experimental result obtained byexamining the proper density of hydrogen in the SiN film constitutingthe buffer layer.

[0240] As shown in FIG. 34, a thin SiN film 92 a having a thickness ofabout 50 nm and then a SiO₂ film 92 b having a thickness of about 200 nmwere formed on a glass substrate 91 through a P-CVD process to form abuffer layer 92. An a-Si film 93 having a thickness of about 150 nm wasthen formed thereon. The thickness of each film is not limited to theabove value.

[0241] Subsequently, the a-Si film 93 was dehydrogenated by a thermaltreatment in a nitrogen atmosphere at 450° C. for two hours. In a SIMSanalysis, it was confirmed that the density of hydrogen in the thin SiNfilm 92 a became 1×10²²/cm³ or less. At this time, the density ofhydrogen in the a-Si film 93 was 1×10²⁰/cm³ or less.

[0242] The a-Si film 93 was then crystallized with asemiconductor-exciting (LD-exciting) solid state laser (DPSS laser)Nd:YVO₄ under conditions of an output of 6.5 W, a scanning speed of 20cm/sec, and a wavelength of 532 nm (the second harmonic of Nd:YVO₄).Scanning was performed by moving the X-Y stage. As a result, a goodcrystal was obtained like in FIG. 36.

[0243] As described above, according to this embodiment, it becomespossible to unformize the transistor characteristics of TFTs at a highlevel using crystallization with an energy beam that outputs energycontinuously in relation to time, and to stably form the TFTs withoutgeneration of pinholes and peeling-off, thereby realizing the veryhighly reliable TFTs.

[0244] In the above-described embodiments, the a-Si film is used as thesemiconductor film. However, the present invention is applicable also toany case wherein the initial film is a p-Si film formed through an LPCVDprocess, a p-Si film by solid phase growth, a p-Si film by metal-inducedsolid phase growth, or the like.

[0245] The present invention can implement TFTs in which the transistorcharacteristics of the TFTs are made uniform at high level, and themobility is high particularly in the peripheral circuit region to enablehigh-speed driving in applications to a peripheral circuit-integratedTFT-LCD, system-on panel, system-on glass, and the like.

[0246] Further, according to the present invention, it becomes possiblethat the insufficiency of the output of an energy beam, which outputsenergy continuously in relation to time, is compensated so that thethroughput in crystallization of semiconductor films is improved,thereby realizing highly efficient TFTs whose mobility is highparticularly in a peripheral circuit region to enable high-speeddriving.

What is claimed is:
 1. A manufacturing method of a semiconductor devicein which a pixel region and a peripheral circuit region about it areprovided on a substrate, each of said regions being to include thin filmtransistors, said method comprising the steps of: forming asemiconductor film at least in said peripheral circuit region; andcrystallizing said semiconductor film using an energy beam with itsenergy being output continuously in relation to time so that said filmcan serve as an active semiconductor film of each thin film transistor.2. The method according to claim 1, wherein said semiconductor film ispatterned into lines or islands on said substrate.
 3. The methodaccording to claim 2, wherein a marker for positional adjustment ofirradiation with said energy beam is provided on said substrate tocorrespond to each piece of said semiconductor film patterned.
 4. Themethod according to claim 1, wherein slits are formed in saidsemiconductor film and said semiconductor film is irradiated with saidenergy beam being moved in a substantially longitudinal direction ofsaid slits.
 5. The method according to claim 4, wherein neighboringslits in said semiconductor film are apart from each other with thedistance between them gradually changing.
 6. The method according toclaim 4, wherein two slits are formed in said semiconductor film and acrystallized region between them made by irradiation with said energybeam is used as a channel region of a thin film transistor.
 7. Themethod according to claim 1, wherein slender linear insulating films areformed on said semiconductor film and said semiconductor film isirradiated with said energy beam being moved in a substantiallylongitudinal direction of said insulating films.
 8. The method accordingto claim 7, wherein neighboring insulating films on said semiconductorfilm are apart from each other with the distance between them graduallychanging.
 9. The method according to claim 7, wherein two insulatingfilms are formed on said semiconductor film and a crystallized regionbetween them made by irradiation with said energy beam is used as achannel region of a thin film transistor.
 10. The method according toclaim 1, wherein said semiconductor film is patterned on said substrateso as to have portions different in thicknesses.
 11. The methodaccording to claim 10, wherein a thin portion of said semiconductor filmis surrounded by a thick portion of said semiconductor film and saidsemiconductor film is irradiated with said energy beam being moved in alongitudinal direction of said thin portion.
 12. The method according toclaim 10, wherein a channel region of a thin film transistor is formedso as to correspond to said thin portion.
 13. The method according toclaim 1, wherein irradiation with said energy beam in said pixel regionis performed under different irradiation conditions from those in saidperipheral circuit region.
 14. The method according to claim 1, whereina semiconductor film formed in said pixel region is crystallized using apulse energy beam and said semiconductor film formed in said peripheralcircuit region is crystallized using said energy beam with its energybeing output continuously in relation to time.
 15. The method accordingto claim 14, wherein said semiconductor film formed in said peripheralcircuit region is crystallized after said semiconductor film formed insaid pixel region is crystallized.
 16. The method according to claim 1,wherein said semiconductor film formed in said peripheral circuit regionis used for an active semiconductor film after crystallization usingsaid energy beam with its energy being output continuously in relationto time and a semiconductor film formed in said pixel region is used foran active semiconductor film without such crystallization.
 17. Themethod according to claim 16, wherein said semiconductor film formed insaid peripheral region is dehydrogenated using said energy beam with itsenergy being output continuously in relation to time before saidsemiconductor film formed in said peripheral circuit region iscrystallized.
 18. The method according to claim 1, wherein asemiconductor film and a gate oxide film are formed in either of saidpixel region and said peripheral region, at least one of saidsemiconductor film and said gate oxide film of said pixel region beingdifferent in thickness from that of said peripheral circuit region. 19.The method according to claim 1, wherein said energy beam is moved toscan said semiconductor film.
 20. The method according to claim 19,wherein said energy beam being moved along a short side of a rectangularshaped pixel.
 21. The method according to claim 19, wherein the scanningdirection with said energy beam is parallel with the current flowdirection in a portion of an active semiconductor film to serve as achannel region.
 22. The method according to claim 1, whereinsemiconductor films at different positions are irradiated at once usingenergy beams with their energies being output continuously in relationto time.
 23. The method according to claim 19, wherein the scanningspeed with said energy beam is controlled to be not less than 10 cm/sec.24. The method according to claim 1, wherein the output instability ofsaid energy beam is controlled to be smaller than ±1%/h.
 25. The methodaccording to claim 24, wherein the noise (optical noise) indicating theinstability of said energy beam is controlled to be not more than 0.1rms %.
 26. The method according to claim 1, wherein said energy beam isobtained from a CW laser.
 27. The method according to claim 26, whereinsaid CW laser is a semiconductor LD excitation solid state laser. 28.The method according to claim 1, wherein said active semiconductor filmis made using said energy beam into a crystalline state having astreamlined flow pattern with large crystal grains.
 29. The methodaccording to claim 1, wherein said substrate is made of non-alkali glassor plastic and irradiation with said energy beam is performed from theupper or lower side of said substrate.
 30. The method according to claim1, wherein said energy beam is optically split into sub-beams anddifferent portions of said semiconductor film are irradiated with saidsub-beams at once to be crystallized.
 31. The method according to claim29, wherein only a portion where a thin film transistor is to be formedis irradiated with said energy beam or a sub-beam at the optimum energyfor crystallization and a portion where no thin film transistor is to beformed is rapidly skipped.
 32. The method according to claim 1, whereinat least two portions in each of which a thin film transistor is to beformed are crystallized under conditions different in one of thescanning speed, the energy intensity, and the beam shape.
 33. The methodaccording to claim 1, wherein said semiconductor film is intermittentlyirradiated with said energy beam so that only portions where thin filmtransistors are to be formed are crystallized.
 34. The method accordingto claim 33, wherein, during interval of irradiation periods forneighboring portions of said semiconductor film where thin filmtransistors are to be formed, said energy beam is rapidly moved toanother portion where a thin film transistor is to be formed, tocrystallize said portion.
 35. The method according to claim 33, whereinsaid energy beam is intermittently applied to portions where no thinfilm transistor is to be formed so that positioning markers having apredetermined crystallized shape for thin film transistors are formed.36. The method according to claim 1, wherein said semiconductor film isformed over said substrate with a buffer layer being interposed betweenthem, said layer including a thin film containing Si and N, or Si, O,and N, and the density of hydrogen in said semiconductor film iscontrolled to be not more than 1×10²⁰/cm³.
 37. The method according toclaim 36, wherein the density of hydrogen in said thin film iscontrolled to be not more than 1×10²²/cm³.
 38. The method according toclaim 36, wherein dehydrogenation of said semiconductor film isperformed after said semiconductor film is formed or after saidsemiconductor film is patterned.
 39. A semiconductor device comprising:a substrate; a pixel region formed on said substrate and including thinfilm transistors; and a peripheral circuit region about said pixelregion, said peripheral circuit region being formed on said substrateand including thin film transistors, wherein each of activesemiconductor films of said thin film transistors in said peripheralcircuit region is formed into a crystalline state having a streamlinedflow pattern with large crystal grains.
 40. The device according toclaim 39, wherein the grain size of said flow pattern is longer than achannel length.
 41. The device according to claim 40, wherein saidactive semiconductor films have been formed by applying an energy beamto semiconductor films patterned on said substrate into lines orislands.
 42. The device according to claim 41, wherein markers forpositional adjustment of irradiation with said energy beam are providedon said substrate to correspond respectively to said semiconductor filmspatterned.
 43. The device according to claim 39, wherein said activesemiconductor films in said peripheral circuit region are different inthickness from active semiconductor films in said pixel region.
 44. Thedevice according to claim 39, wherein said substrate is made of oneselected from the group of non-alkali glass, quartz glass, ceramic,plastic, and monocrystalline silicon with amorphous insulating film. 45.The device according to claim 39, wherein a semiconductor film is formedover said substrate with a buffer layer being interposed between them,said layer including a thin film containing Si and N, or Si, O, and N,and the density of hydrogen in said semiconductor film is not more than1×10²⁰/cm³.
 46. The device according to claim 45, wherein the density ofhydrogen in said thin film is not more than 1×10²²/cm³.
 47. The deviceaccording to claim 45, wherein said buffer layer has a structure ofSiO₂/SiN or SiO₂/SiON.
 48. A semiconductor manufacturing apparatus foremitting an energy beam for crystallizing a semiconductor film formed ona substrate, wherein said apparatus can output said energy beamcontinuously in relation to time and has a function of relatively movingsaid energy beam to scan a target to be irradiated, and the outputinstability of said energy beam is smaller than ±1%/h.
 49. The apparatusaccording to claim 48, wherein said energy beam being moved along ashort side of a rectangular shaped pixel.
 50. The apparatus according toclaim 48, wherein the noise (optical noise)indicating the instability ofsaid energy beam is not more than 0.1 rms %.
 51. The apparatus accordingto claim 48, wherein the scanning speed with said energy beam is notless than 10 cm/sec.
 52. The apparatus according to claim 48, whereinsaid apparatus can emit an energy beam with its energy being outputintermittently.
 53. The apparatus according to claim 48, wherein saidenergy beam is obtained from a CW laser.
 54. The apparatus according toclaim 53, wherein said CW laser is a semiconductor LD excitation solidstate laser.
 55. The apparatus according to claim 48, wherein saidapparatus reads and memorizes the position of a marker, which isprovided on said substrate, for positional adjustment of irradiationwith said energy beam, and performs irradiation with said energy beam inaccordance with said position.
 56. A semiconductor manufacturingapparatus comprising: disposing means for carrying thereon a substrateon a surface of which a semiconductor film is formed, so that saidsubstrate can freely be moved in a plane parallel with a surface of saidsemiconductor film; laser oscillator having a function of outputting anenergy beam continuously in relation to time; and beam splitter foroptically splitting said energy beam emitted from said laser oscillator,into sub-beams, wherein predetermined portions of said semiconductorfilm are relatively scanned with each of said sub-beams to crystallizedsaid predetermined portions.
 57. The apparatus according to claim 56,wherein said energy beam being moved along a short side of a rectangularshaped pixel.
 58. The apparatus according to claim 56, wherein only aportion where a thin film transistor is to be formed is irradiated witheach of said sub-beams at the optimum energy for crystallization and aportion where no thin film transistor is to be formed is rapidlyskipped.
 59. The apparatus according to claim 56, wherein each of saidsub-beams is applied such that at least two portions in each of which athin film transistor is to be formed are crystallized under conditionsdifferent in one of the scanning speed, the energy intensity, and thebeam shape.
 60. The apparatus according to claim 56, wherein each ofsaid sub-beams is applied so as not to overlap each other.
 61. Theapparatus according to claim 56, wherein the output instability of saidenergy beam is smaller than ±1%/h.
 62. The apparatus according to claim61, wherein the noise (optical noise)indicating the instability of saidenergy beam is not more than 0.1 rms %.
 63. A semiconductormanufacturing apparatus comprising: disposing means for carrying thereona substrate on a surface of which a semiconductor film is formed, sothat said substrate can freely be moved in a plane parallel with asurface of said semiconductor film; laser oscillator having a functionof outputting an energy beam continuously in relation to time; andintermittent emission means having a transmission area and aninterruption area for said energy beam so as to allow said energy beamto pass intermittently, wherein, as said substrate is relatively scannedwith said energy beam, said semiconductor film is intermittentlyirradiated with said energy beam so that only portions where thin filmtransistors are to be formed are selectively crystallized.
 64. Theapparatus according to claim 63, wherein said energy beam being movedalong a short side of a rectangular shaped pixel.
 65. The apparatusaccording to claim 63, wherein, by controlling scanning speed on saidsubstrate and timings for intermittent emission by said intermittentemission means, during interval of irradiation periods for neighboringportions of said semiconductor film where thin film transistors are tobe formed, said energy beam is rapidly moved to another portion where athin film transistor is to be formed, to crystallize said portion. 66.The apparatus according to claim 63, further comprising beam splitterfor optically splitting said energy beam emitted from said laseroscillator, into sub-beams, wherein, as said substrate is relativelyscanned with said energy beam, said semiconductor film is intermittentlyirradiated with each of said sub-beams so that portions where thin filmtransistors are to be formed are crystallized at once.
 67. The apparatusaccording to claim 63, wherein said energy beam is intermittentlyapplied to portions where no thin film transistor is to be formed sothat positioning markers having a predetermined crystallized shape forthin film transistors are formed.
 68. The apparatus according to claim63, wherein the output instability of said energy beam is smaller than±1%/h.
 69. The apparatus according to claim 68, wherein the noise(optical noise) indicating the instability of said energy beam is notmore than 0.1 rms %.
 70. A manufacturing method of a semiconductordevice comprising a substrate and semiconductor elements on saidsubstrate, said method comprising the step of: crystallizingsemiconductor films of said semiconductor elements with an energy beamwith its energy being output continuously in relation to time.
 71. Themethod according to claim 70, wherein said semiconductor films areformed into a line or island pattern and irradiated with said energybeam.